Method for the production of a forged piston for an internal combustion engine

Abstract

A method for the production of a forged piston for an internal combustion engine, having a combustion depression provided on the piston head. The piston is formed from a first cylindrical unmachined part having at least one flat face made of oxidation-resistant steel and a second cylindrical unmachined part having at least one flat face made of hot-forgeable steel, with the same diameters (d), in each instance. The two unmachined parts are formed to produce a piston blank by means of forging, causing the combustion depression to be formed from oxidation-resistant steel. Subsequently the piston blank is finished via machining to produce a piston ready for installation in the internal combustion engine. Production of a piston having a reduced tendency to oxidize at the edge of the depression, and improved protection against wear caused by erosion, which is simple cost-effective, is achieved in that the unmachined parts are brought together at their faces and aligned with respect to their diameters, so that the faces form a minimal projection and parting. Subsequently, the parting is completely closed from the outside, by a weld seam that runs over the circumference.

What is claimed is:  
     
         1 . A method for the production of a forged piston for an internal combustion engine, the piston having a combustion depression provided on the piston head, comprising the steps of: 
 forming the piston from a first cylindrical unmachined part having at least one flat face made of oxidation-resistant steel and a second cylindrical unmachined part having at least one flat face made of hot-forgeable steel, with the same diameters, to produce a piston blank by forging, said step of forming comprising: 
 bringing together the unmachined parts at their faces and aligning them with respect to their diameters, so that the faces form a minimal projection and parting; and  
 closing the parting completely from the outside, by producing a weld seam that runs over the circumference;  
 causing the combustion depression to be formed in the oxidation-resistant steel, and  
 finishing the piston blank via machining to produce a piston ready for installation in the internal combustion engine.  
   
     
     
         2 . The method according to  claim 1 , wherein the parting is closed by welding at room temperature or in a heated state of the unmachined parts.  
     
     
         3 . The method according to  claim 2 , wherein before forging, the unmachined parts, which have been welded together, are heated to a temperature of 1100° C. to 1300° C., and the unmachined parts subsequently forged to produce the piston blank, in the heated state.  
     
     
         4 . The method according to  claim 3 , wherein the heating takes place inductively.  
     
     
         5 . The method according to  claim 2 , wherein the welding is arc welding, laser welding, or electron beam welding.